Coated articles and IG window units are known in the art. For example, see U.S. Pat. Nos. 5,514,476, 5,800,933 and 6,014,872.
Commonly owned U.S. Patent Application Publication No. 2003/0150711 (hereby incorporated herein by reference) discloses a coated article as follows, from the glass substrate outwardly (the top tin oxide layer may be omitted in certain instances) with example thicknesses listed in units of angstroms (Å):
TABLE 1Example Coating of 2003/0150711LayerPreferredMoreExampleGlass SubstrateRange (Å)Preferred (Å)(Å)TiO20-700Å100-400Å200ÅZnOx25-200Å40-150Å90ÅAg50-250Å80-200Å130ÅNiCrOx5-100Å15-60Å30ÅSnO20-1,000Å500-900Å680ÅZnOx25-200Å40-150Å90ÅAg50-250Å80-220Å168ÅNiCrOx5-100Å15-60Å30ÅSnO20-500Å70-200Å125ÅSi3N40-500Å120-320Å220Å
When the aforesaid coated article is coupled with another glass substrate in order to make an IG window unit, the resulting IG window unit (not heat treated (HT)) generally has the following optical characteristics (Ill. C, 2 degree observer):
TABLE 2Optical Characteristics of IG Window Units with Above Coating(non-HT)CharacteristicGeneralMore PreferredTvis (or TY) (transmissive):>=69%>=70%a*t:−6.0 to +1.0−5.0 to −2.0b*t:−1.0 to 4.0  0.5 to 3.5RgY (glass side):    5 to 15%    8 to 12%a*g:−4.0 to +2.0−3.0 to −1.0b*g:−4.0 to +2.0−3.0 to +1.5L*g:   34 to 42   36 to 40RfY (film side):    5 to 18%    9 to 15%a*f:−5.0 to +4.0−3.0 to +2.0b*f:−8.0 to +8.0−5.0 to +6.0L*f:   33 to 48   35 to 45
In Table 2 above, Tvis stands for visible light transmission, and a*t and b*t stand for transmissive (t) a* and b* color values, respectively. Glass side (g) and film side (f) values are presented in a similar manner. It is noted that the color values herein (e.g., a*, b*, L*) are calculated in accordance with the CIE LAB 1976 L*, a*, b* coordinate technique.
The IG units of Tables 1-2 (and thus 2003/0150711) are not heat treated (HT). However, in commercial applications, at least some IG units often are required to be heat treated (e.g., tempered) for safety purposes. In office buildings for example, it is often desirable that some windows be heat treated while others need not be. Thus, a need for matchability (before heat treatment vs. after heat treatment) arises. In other words, it is desirable that window units which are heat treated (HT) substantially or approximately match their non-heat treated counterparts (e.g., with regard to color, visible transmission, reflectance, and/or the like), at least with respect to transmissive and glass side reflective optical characteristics, for architectural and/or aesthetic purposes.
Unfortunately, coatings of 2003/0150711 cannot withstand HT without significant color and/or durability change. Thus, coatings of 2003/0150711 cannot be HT and then used commercially to achieve matchability with their non-HT counterparts.
It will be apparent from the above that there exists a need in the art for coatings that, upon HT, approximately matches non-HT coatings of 2003/0150711 in the context of IG window units with regard to visible transmission, visible reflectance, transmissive color, and/or glass side reflective color.
While coatings having multiple infrared (IR) reflecting Ag layers are desirable in certain instances, they tend to have very low sheet resistance (Rs) values thereby making them difficult to easily HT (without resulting in damage or becoming prohibitively costly) using inexpensive HT processing/machinery. This is because the dual Ag layers tend to reflect much of the energy in the furnace intended for tempering the underlying glass substrate. Single silver coatings, with higher sheet resistances, are easier to HT in this regard. Thus, in certain example non-limiting instances it would be desirable for coatings herein to achieve the aforesaid matchability and/or be of the single Ag layer type (or have higher Rs) so that they can be more easily heat treated using conventional low-tech radiant tempering furnaces.
U.S. Pat. Nos. 5,514,476 and 5,800,933 discloses coated articles including: glass substrate/Si3N4/NiCr/Ag/NiCr/Si3N4. Unfortunately, upon HT and use in an IG unit, the resulting IG units do not approximately match the general aforesaid optical characteristics of IG units set forth in Table 2.
WO 02/04375 discloses a dual-silver low-E coating have good color characteristics after HT and lamination. Unfortunately, the coatings of WO 02/04375 require multiple silver (Ag) layers and have very low sheet resistance (Rs) (e.g., about 4-5 ohms/square) before HT. This makes the coatings of WO 02/04375 difficult to HT using conventional low-tech radiant tempering furnaces since the dual Ag layers reflect much of the energy intended for tempering the underlying glass substrate. It is noted that WO 02/04375 is a counterpart to U.S. Ser. No. 09/794,224, filed Feb. 28, 2001.
U.S. Pat. No. 6,749,941 (incorporated herein by reference) discloses a coated article made up of the following stack: glass/SiN/NiCr/Ag/NiCr/SiN. This coated article is designed to approximately match that of 2003/0150711 with respect to optical characteristics after being heat treated. However, it would be desirable if the solar performance (e.g., SHGC, sheet resistance and/or emissivity), ultraviolet (UV) transmission, and/or thermal stability of the coated article of the '941 patent could be improved without sacrificing the coated article's ability to approximately match that of 2003/0150711 with respect to color and transmission characteristics following heat treatment.
An object of certain example non-limiting embodiments of this invention is to provide a coating that, upon HT and in the context of IG window units, approximately matches an IG unit including a non-HT coating of 2003/0150711 (see general desired optical characteristics in Table 2 above) with respect to visible transmission (Tvis), visible glass side reflectance (RgY), transmissive color (a* and/or b*), and/or glass side reflective color (a* and/or b*).
Another object of certain example non-limiting embodiments of this invention is to provide a single silver (Ag) coating (i.e., including only one Ag layer) that, upon HT and in the context of IG window units, approximately matches an IG unit including a non-HT coating of 2003/0150711 with respect to visible transmission (Tvis), visible glass side reflectance (RgY), transmissive color (a* and/or b*), and/or glass side reflective color (a* and/or b*).
In certain example embodiments of this invention, it would be desirable for the coating, before and/or after HT, to have a sheet resistance (Rs) of no more than about 10 ohms/square, more preferably no more than about 8 ohms/square, even more preferably no more than about 6 ohms/square, and most preferably no more than about 5 ohms/square. In certain example embodiments, the coating has only one Ag layer.
It has surprisingly been found that the use of a coating including a stack: glass/SiN/ZnO/Ag/NiCr/SiN can be tailored to result in a coated article that can achieve remarkably lower sheet resistance, remarkably lower UV transmission characteristics, and improved thermal stability upon HT compared to coatings of U.S. Pat. No. 6,749,941, while still being able to approximately match after HT coated articles of U.S. Patent Publication No. 2003/0150711 with respect to visible transmission (Tvis), visible glass side reflectance (RgY), transmissive color (a* and/or b*), and/or glass side reflective color (a* and/or b*).
In certain example embodiments, it is optionally possible to use a layer of Si-rich (non-stoichiometric) silicon nitride as the bottom silicon nitride inclusive layer in order to help achieve certain desired color characteristics (whether corresponding to non-HT coatings of 2003/0150711 or not). In certain example non-limiting embodiments, it is possible to provide a heat treatable coating that includes a non-stoichiometric silicon nitride layer, wherein the amount of Si in the layer is adjusted (i.e., increased relative to stoichiometric Si3N4) so as to increase the layer's index of refraction “n” and/or extinction coefficient “k”, in order to achieve desired optical characteristics.
In certain example embodiments of this invention there is provided a insulating glass (IG) window unit comprising: first and second glass substrates spaced apart from one another so that a space is provided therebetween, at least the first glass substrate being thermally tempered and supporting a coating, wherein the coating comprises: a first dielectric layer comprising silicon nitride, a lower contact layer comprising zinc oxide, a layer comprising Ag, an upper contact layer, wherein the layer comprising Ag is located between and directly contacts each of said upper and lower contact layers, and a second dielectric layer, wherein the IG window unit has a SHGC of no greater 0.55, a visible transmission of at least about 68%, transmissive a* color of from −5.5 to 0.0, transmissive b* color of from +0.5 to +3.5, glass side reflective a* color of from −4.0 to +2.0, and glass side reflective b* color of from −4.0 to +3.0.
In certain other example embodiments of this invention, there is provided a insulating glass (IG) window unit comprising: first and second glass substrates spaced apart from one another so that a space is provided therebetween, at least the first glass substrate supporting a coating and being thermally tempered, wherein the coating comprises: a first dielectric layer, a lower contact layer comprising zinc oxide, a layer comprising Ag, an upper contact layer, wherein the layer comprising Ag is located between and directly contacts each of said upper and lower contact layers, and a second dielectric layer, wherein the IG window unit has a SHGC of no greater 0.55, glass side reflective a* color of from −3.0 to +1.0, glass side reflective b* color of from −3.0 to +1.5.